Gear lapping machine



Jan. 9, 1940. E. R. NYLAND' GEAR LAPPING MACHiNE Filed Sept. 29, 1937 ll Sheets-Sheet l 3 idl /W172 fly/422d Jan. 9, 1940.

E. R. NYLAND GEAR LAPPING MACHINE 11 Sheets-Sheet 4 Filed Sept. '29, 1957 Jan. 9, 1940. E. RQNYLAND GEAR 'LAPPING MACHINE Filed Sept: 29. 1957, 11 Sheets-Sheet s 'dmdQWy/mzd y y Wk GEAR LAPPING MACHINE Filed Sept. 29, 193? 1'1 Sheets-Sheet 6 Jan. 9,1940. E. R. NYLAND 7 2,186,304

nventor Jan. 9, 1940;

E. R. NYLAND GEAR LAPPING MACHINE Filed Sept. 29, 1937 11 Sheets-Sheet 8 Jan. 9, 1940.

E. R. NYLAND GEAR LAPPING MACHINE Filed Sept. 29, 1937 11 Sheets-Sheet 9- Jan. 9, 1940. E. R. NYLAND GEAR LAPPING MACHINE 11 Sheets-Sheet 10 .Filed Sept. 29, 1937 Jan. 9, 1940.

1 E. R. NYLAND I GEAR LAPPING MACHINE Filed Sept. 29, 1937 ll SheetS -Sheet 11 (Eda/442% UNITED STATES.

PATENT OFFICE! GEAR LAPPING MACHINE Edward R. Nyland, Detroit, Mich assi'gnor to General Motors Corporation, Detroit,'Mich., a corporation of Delaware Application Claims.

This invention relates to the art of finishing gears and the like, and particularly to a machine 01 finishing gears by means of a lapping operaion.

Certain inaccuracies may occur inthe surfaces or contours of gear teeth during their manufacture as a result of the gear cutting operation or in the warping or distortion incident to the subsequent heat treatment thereof. In order to smooth and true up the gear teeth it is customary to finish the gears by means of a lapping opera- I tion. The primary object of this invention is to provide an improved machine for lapping gears and the like.

Another object or this invention is to provide a gear lapping machine that is highly eflicient and rapid in operation and of simple construction.

I It is also an object of this invention to provide an improved machine for lapping helical gears.

Still another object of this invention is to provide a gear lapping machine in which a simplified means is provided for quickly adjusting the machine for gears having different helical angles.

A further object of this invention is to provide a means of simple construction for moving the upper and lower centers of .a gear lapping machine as a unit.

Another object is to provide a simplified means for quickly moving the upper center unit with re-' spect to the lower center unit.

It is also an object of this invention to provide an improved angle adjusting means for changing the angle at which 'a gear is supported with respect to a lapping ring. in order to remove a greater or less amount of material at either end of the teeth of the gear being lapped. I

Other objects and advantages of this inventionreside in various simplified adjusting means whereby the lapping machine may be quickly adjusted to meet variable conditions of operation.

Other objects and advantages of my invention will become more apparent as the description proceeds. Reference is herein made to the accompanying drawings forming a portion of this specification, in which: v

Figure l is a side elevation of the complete machine.

Figure 2 is a front elevation of the machine illustrated in Figure 1.

' Figure 3 is a partial sectional view substantially on line 3-3 in Figure 1.

Figure 4 is a sectional view on line H in Figure zshowing the lapping ring and associated parts.

September 29, 1937; Serial No. 166,245

Figure 5 is a view substantially on line 5 5 in Figure 4 with parts broken away in order to show the construction more clearly.

Figure 6 is a view online 66 in Figure 1 showing means to resiliently secure in place the 5 lower center unit;

Figure 7 is a sectional view on line in Figure 6 showing the constructionof one of the members which resiliently secures the lower center unit in place.

Figure 8 is a view on line 88 in Figure 2 showing the relationship of the parts of the upper ,center unit of .the' machine which oscillate the gear to be lapped.

Figure 8a is a sectional view-substantially on 15 line 8a-8a' in Figure 8 showing an adjusting means.

Figure 9 is a view taken on-line 9-9 in Figure 8.

Figure 10 is a detail view on line I0l0 in Fig- 20 ure 9. v

Figure ll is a view on line "-4 I in Figure 2 showing adjusting means.

Figure 12 is a view taken Figure 11. I e 25 Figure 13 is a detail view-taken on line l3l3 in Figure 11. I

Figure 14 is a sectional view on line l4|4 in Figure 2. a v

Figure 15 is a view on line |5l5in Figure 14. 30 Figure 16 is a detail sectional view on line l6-l' 6 in Figure 14.

Figure 17 is a detail view with parts in section taken on line 11-11 in Figure 5.

Figure 18 is a detail view on line .l8l8 in 35 Figure 5.

Figure 19 is a detail view of a gear. to be lapped mounted on an arbor therefor.

' Figure 20 is a detail sectional view on line 2020 in Figure 18. 4 The embodiment of the invention shown-in the drawings comprises a lapping ring having internal helical teeth formed therein. It will be understood, however, that the gear to be lapped may be a ring gear having internalteeth and the. lap

may have external teeth. The'lap is adapted to be rotated in mesh with a gear. to be lapped. The lapping ring is rapidly reciprocatedwith re? spect to the'vgear which causes relative sliding motion between the contacting teeth of the gear 50 and lap. A suitable lapping compound is played on the lap and gear during .the lapping operation. The gear and lap have a different numJ- 1 her of teeth so that as' the gear is driven by .engagement with the teeth of the lapping ring; it

provides for more accurate work since different teeth of the lapping ring and gear will thus be brought in contact with each other. Means are provided whereby'the'reciprocation of the lapping ring causes the gear to be moved or rocked through an angle determined by the lead of the helical teeth of the lapping ring and gear in timed relation with the reciprocation. ,Certain features of the machine comprising the subject matter of the present invention are somewhat similar to those of the machine shown and claimed in my copending application, Serial No. ,6,288, filed February 13, 1935, now Patent No. 2,108,547, dated February 15, 1938.

In Figures 1 and 2 of the drawings, the base of the machine is indicated at 2. Supported by the base of the machine is a main supporting frame 4, from the upper end of which is adjustably supported a hollow shaftG; see also Figure 11. The hollow shaft 6 supports an upper center unit indicated generally at 8 and a lower center unit indicated generally at I8. Both of the units are adapted to be secured to the hollow shaft 8 so that they may be raised and lowered with the shaft as a unit.

The lower center unit is best seen in Figures 3 and 4. Secured to the lower portion of the hollow shaft 6 is a supporting member I2 having a trough portion I 4, adapted to return lapping com- 4 pound to the tank therefor, and a sleeve portion I 6. Secured to the sleeve I6 by means of threaded rod l8, washer 28 and nut 22 is a flanged sleeve 24, the flange of which rests on the end of sleeve I8. Within the flanged sleeve 24 is rotatably mounted a spindle 26" having a lower center 28 formed with a conical end 38. adapted to engage one end of an arbor 32 to which is secured a gear 34 to be lapped. v'I'he lower center 28 is tapered and frictionally engages a tapered opening 38 formed in the upper end of the spindle 28.

Secured to the upper end of the spindle, as by means of the threaded connection 38, is a cover 48 having'a downwardly extending sleeve portion 42 which protects the bearings from the lapping compound. A sleeve 44, having a' flange portion 46 engaging a mating flange on the spindle and a threaded portion 48 engaging the upper-portion of the flanged sleeve 24, prevents the spindle from being moved an excessive amount, although allowing the spindle to rotate within the sleeve. Suitable bearings 58 and 52 rotatably support the spindle.

Surrounding the spindle 28 and associated parts is a larger sleeve 54 having a flange at its upper end .to which is fixed a lapping ring 58 by .means of retainer 53. A cap 55 is also secured to the flange of the sleeve, as best seen in Figure 4. 'The sleeve 54 is adapted to be reciprocated by means of the yoke 58; see also Figure'5. The branches of the yoke embrace the sleeve and are connected by diametrically opposite pins 51 to a member 6| secured to the sleeve as will be readily understood from Figure 4. The sleeve is rotated by means of a worm 58 and a worm gear 88 which acts as a stop or support for a circular series of coiled springs 88, 88. Th other ends of the springs are mounted in a corresponding circular 2,188,304 rotates with respect to the lapping ring. This aligned pockets I2 formed in the lower surface of the ring gear and cup-shaped members I4 secured to the lower portion of the sleeve. By means of the several springs excessive roughness or vibration due to the rapid rate of reciprocation of the sleeve and parts carried thereby will be obviated.

Reciprocation of the sleeve 54 actuates a rod I6 connected at one end by a ball and socket joint I8 with a portion of the yoke; As best seen in .Figures 8 and 9 the upper end 01' the rod has a rack portion 88 adapted to mesh with, and rock back and forth, the gear 82. The rack portion is of suflicient length to remain in mesh with the gear during movement of the upper center unit with respect to the lower. Secured to the gear is a member 88 having an arcuate portion 84 formed with a T-slot 86 therein. Within the T-slot is a nut 88 having sides curved to flt the arcuate curve of the T-sl'ot. A stud 89 having a ball 9| at one end thereof engaging a socket in one end of a connecting rod 88 also-has a screw threaded connection 93 at its opposite end with the nut 88. It will be understood that the nut 88 is movable within the slot when the stud is unscrewed and will be fixed in any desired position of adjustment during operation of the device by screwing the stud into the nut 88 until the nut portion 95 of the stud engages the arcuate member.

The arcuate member may be calibrated to coirespond to the helical angle of the gear to be lapped and the adjustment described is to permit gears having different helical angles to be lapped. The member 83 and gear 82 are carried by a bracket 228 and supported therein by bearings 22I. The bracket, in turn is secured by vmeans of screws 222 to a projecting portion 228 of the frame of the upper center unit. The-opposite end of the connecting rod has a yieldable ber 88. A circular series of coiled springs I88 are mounted between the bottom of the cup-portion and an annular disc I88. Aligned pockets I I8 and H2 formed in the annular disc and cupportion respectively receive the opposite ends of the several springs and maintain the springs in position as will be readily understood from Figures 14 and 16.

Projections II4 on the annular disc engage mating slotsl I6 formed in the sides of the cupportion 188. A clutch disc I22 havin'g friction material I28 on either side thereof slidably engages the annular disc I 88 and is held yieldably in contact therewith by means of the circular series of coiled springs. The clutch disc has a series of inwardly projecting portions II8 within corresponding slots I24 formed in'a' sleeve I28 fixed to a spider I 28. A second annular disc I88 contacts the opposite-side of the clutch disc and has outwardly extending projections I82 engaging the slots H8. By means of the member I84 having a screw-threaded connection I38 with the sides of the cup-shaped portion I88 of member 98 the clutch disc and annular discs which contact both sides of the clutch disc can be moved toward or away from the bottom of. the cupshaped portion in order to vary the force of the coiled springs. In this way the pressure on the friction material of the clutch disc may be varied 1| in the several arms of the spiders.

and as a consequence the pressure on the engaging teeth of the lap and gear varied. A look vBetween the arms of the spider members are a series of coiled springs I44; see Figure 15. These springs fit within suitable openings I46 formed Screw means I48 are adapted to vary the compressive force of the several springs as will be readily understood. The spring arrangement between the arms of the spiders takes up shock and also compensates for any inaccuracy in the'helical angle adjustment. A nut I50 secures the spider in'position on shaft I42. A cover I52 is hinged at I54 to the frame of the-upper unit.

As best seen in Figure 8 the lower end of shaft I42 has a tapered opening I56 in which is a tapered spindle I58 having a conical tip I60 adapted to engage one end of the arbor 32 on which the gear to be lapped is mounted. Suitable bearings I64, I66 in the frame of the upper .center unit supportthe shaft I42 for rotation therein. A coupling I68 having notches I10 in its lower portion engages a pin I12 in the upper end of the arbor to drive the latter.

In order to move the upper center unit with respect to the lower, there are provided an air cylinder, or otheigasuitable hydraulic means, and members actuated thereby, which are illustrated in Figures 1, 2, 8, 9 and 10. In these figures, I14 is an air cylinder secured to the frame I04 'of the upper center unit within which cylinder is a suitable piston I16 secured to one end of a. rod I18. Compressed air, or other fluid, is admitted to the cylinder through the pipe I80 and forces the piston and rod downwardly. The lower portion of the rod has a rack portion I82 which engages with a gear I84 mounted on a tubular shaft I86 in the frame of the upper center unit.

The gear is normally fixed against rotation on shaft I86 by means of member I88 having clutch teeth I80 thereon which engage mating slots formed by clutch teeth I8I on the gear. Member I88 is keyed at I82 to the hollow shaft I86 having gear teeth I86 formed thereon engaging rack teeth I88 on the hollow shaft 6.

The frame of theupper center unit is splined at' I80 to the hollow shaft 6 and hence downward movement of the rack portion I82 of the piston rod I18 will rotate shaft I86 and gear teeth formed thereon and cause the upper center unit to move "upwardly along the hollow shaft 6. When air, or other fluid, is exhausted from the cylinder I14 the weight of the upper unit in cooperation with a spring 200 surrounding rod I18 will lower the upper center unit.

In order to permit the upper center 'unit to be moved by hand for adjustment purposes without the use of the air cylinder means the mechanism now to be described is used. Within the hollow shaft I86 is a rod 202 having a threaded end portion 204 on which is a nut 206 which secures the rod to the shaft. A pin 208 extending through the opposite end of the rod has its opposite ends'extending into clutch member I 88 and is slidable withinj slots 2I0 formed in the hollow shaft. By removing nut 206 the rod 202 and clutch member I88 may be moved to the left as viewed in Figure 10 to disengage the clutch teeth I80 of clutch member I88 and the teeth I8I on the gear. One end of the hollow shaft I86 has a portion 2I2 adapted to be'engaged by a wrench, or other tool, whereby the hollow shaft may be rotated without the air cylinder means.

The rack 80 which rocks the gear 82 back and forth in timed relation with the reciprocation of the lapping ring has its rear side engaging a flanged roller 2 I4 which is rotatably mounted on a pin 2I6. The pm extends through one end of a rod 2I8, see Fig. 8, which has a portion 2I8 engaging a cutout portion 224 of the bracket 220. The rod extends through an opening in the bracket and has a nut and washer 228 at the free end thereof. A coil spring 230 surrounding the rod 2I8 has one end contacting the washer and the other end contacting a flat surface 232 of the bracket. biases the rod 2 I8, pin 2I6, roller 2I4 in a direction to resiliently hold the rack in engagement with the gear. For adjustment purposes an eccentric 234 is provided whereby movement thereof will move the rod 2I8 and associated parts against the force of spring 230 to enable the rack teeth to disengage the gear teeth.

In Figures 1, 2, 11, 12 and 13 there is shown a The spring is under compression and and having a flange portion thereof secured to the hollow shaft is a member 236. The latter has an internal threaded portion 238 into which extends the threaded end 240 of a rod 242 having a gear'244 at its opposite end. A stub shaft 246 has a portion 248 at one end, adapted to be engaged by a wrench, and a gear 250 at its other end engaging the gear 244. Thus the hollow shaft 6 is supported from the top of the main frame by the rod 242 and may be raised and low- -ered by means of the stub shaft and gears. The upper andlower center units will be moved therewith. A suitable ball or other bearing 252 is provided in the top of frame for rotatably supporting the rod therein.

What may be termed an angle adjusting means is disclosed in Figures 1, 2, 3, 11, 12 and 13. A collar 254 surrounds the upper end of the hollow shaft 6 and has two ears 256 on the side toward the front of the machine. A pin 258 pivotally secures one end of a threaded rod 260 to the ears of said collar as best seen in Figures 11' and 12. The threaded portion of the rod has engagement with a threaded bushing 262 in the frame of the machine. The bushing is secured to the frame by means of a flanged collar 265 secured to the frame by means of screws 266. The flanged portion of the collar engages a flange 268 on said bushing. On the bushing 262 is a collar 210 which has a circular series of cutaway portions 212 adapted to contact the beveled head 214 of a screw 216. The collar is secured to the bushing by means of a screw 218.

In order to move the threaded rod within the bushing, the screw 216 is loosened until the head is free of a cutaway portion 210, whereupon the bushing may be rotated, as by means of a suitable wrench applied to the squared end 218 thereof; Sincethe bushing is flxed against loncause the threaded rod to move in or out and thus move the upper end of the hollow shaft.

gitudinal movement, rotation of the bushing will the pivot as shown in these figures is substantially at the plane of the top of the lapping tool. The pivot comprises two stub shafts 2,82 and 284 mounted in the frame of the machine extending within mating openings 285 and 288 formed in a collar 298 surrounding the hollow shaft 6. Between the collar and hollow shaft is a bushing 292 which is formed of any suitable material resistant to wear. Movement of the hollow shaft 6 about the pivot will permit the axis of the shaft to be varied with respect to that of the sleeve 54 and the lapping ring mounted thereon. In this way the machine may be adjusted to remove a greater or less amount of material at either end may be resiliently held in contact with the lapping ring. The adjustable means is shown in Figures 1, 2, 5, 6 and 7. In both sides of the lower portion of the frame or casing of the machine is a hollow member 294 having screw threaded engagement at 295 with the frame.

Within the hollow portion of the member 294 is a T-member 295, the head of which contacts the frame of the lower center unit and the leg of which is hollow and has a coil spring 298 therein which biases the frame of the lower center unit to the right as viewed in Figure 7-. An adjusting screw 388 acts as a stop for a plug 382 which contacts one end of the coil spring 298. By this means the compression of the coil spring may be varied as desired. A look nut 384 secures each of the hollow members 234 and parts carried thereby in adjusted positions. The two members 294 and associated parts may be moved and thus cause the centers and arbor which supports the gear to be moved into operative position with respect to the lapping ring. When in the desired position the lock nuts will secure members 294 in place and the resiliently mounted T-members will provide a resilient support for the centers.

The mechanism whereby'the sleeve 54 which supports the lapping ring is reciprocated, is best seen in Figures 4, 5, 17, 18 and 20. A motor 3l8 rotates a shaft M2 by means'of a belt 3 which connects pulleys 3 l6 and M8 mounted on the mo-.

tor shaft and shaft 3|2, respectively. On one end of the shaft 3 i 2 is an enlargement328 having a cutaway portion within which is adjustably mounted a slide block 322 carrying a stub shaft 334. "A screw-threaded member 325 has a flange 328 thereon within a mating opening 338 formed in a member 332 secured to member 328'by means of screws 334. The screw-threaded member is connected to the slide block in order to move the same with the stub shaft 324 canied thereby.

It will be understood that the flange 328 holds 'the screw-threaded member 326 against moveend of an arm orconnecting rod 338. The other end of the arm carries a roller bearing 348 within which is a pin-connection 342' with an arm 344 formed as a portion of'the yoke 58. The yoke is pivoted'on a shaft 345 and thus move- 'may be the lapping tool.

ment of the arm 344 will cause the sleeve 54 and lapping ring to be rapidly reciprocated.

The worm 59 which rotates the gear 58 is driven by means .of a motor 348. A suitable belt 358 connects a pulley on the motor shaft with a pulley secured to a' shaft 352 on whichthe worm is fixed. Preferably the motor 348 is a reversible motor and by means of suitable controls (not shown) will rotate in one direction for a desired period and then will be reversed. In this way the sleeve 54 and lapping ring will first rotate in one direction and then in the other. Preferably, also, the movements in one direction will be greater than that in the other.

In Figures 1, 2 and 6 of the drawings is seen a device whereby the abrasive particles of the lapping compound may be mixed with the liquid portion when beginning a lapping operation after the machine has been standing idle for a time. A handle 358 pivoted at 352 with an arm leading to a grill 364 mounted in the bottom of the tank for the lapping compound is adapted to be moved back and forth to reciprocate the grill to thoroughly agitate the lapping compound. When the device is in operation a suitable pump (not shown) will cause the compound to be forced onto the gear and lap. 'I'he 'compound will then pass downwardly through the sleeve 54 and the trough i4 and be returned to the tank. The flow of lapping compound into the tank from the trough l4 will agitate the lapping compound sufficiently to maintain the abrasive particles in suspension.

The description of the operation of the device will be clear from the foregoing detailed description of the device. This may be briefly summarized as follows: The operator will first mount the gear to be lapped in any suitable fixture and then place the same in the machine between the upper and lower center units. The lapping tool or lapping ring in the embodiment shown is then rapidly reciprocated to cause a relative sliding movement between the gear and lap. The rack driven by this reciprocatory movement causes the oscillation of the gear through an angle determined by the lead of the teeth of the gear and lap. If desired, to adjust the machine for a different helical angle, all that is necessary is to move the nut within the T slot of the armate member. For rapidly and efliciently moving the upper center unit with respect to the lower the fluid operated means is provided. If desired friction between disc I22 and discs I88 and I38.

From the above it will be seen that I have provided a device for lapping gears that is readily adjustable for different sized gears and for gears having different helical angles. It will be understood that many different fixtures than the arbor disclosed may be used to support the gears to be lapped. Likewise the member described as the lapping ring may be a gear to be lapped and the member described as the gear lapping tool and gear may be reversed.

While the preferred form of the machine of this invention is a vertical type machine, it will be understood that certain features of the In other words, the

, thereon except as necessitated by the prior art.

I claim:

1. In a gear lapping machine, a lap, means for supporting said lap, means for supporting a helical gear in mesh with said lap, means for rotating one of said lap supporting and gear supporting means, said means for rotating one of said lap supporting and gear supporting means rotating the other of said lap supporting and gear supporting means through interengagement of the lap and gear, means for reciprocating said means for rotating one of said lap supporting and gear supporting means, and means for rocking the helical gear through an angle determined by the lead of the teeth of the lap and gear in timed relation with the reciprocation of said rotated means comprising, a rack connected with the reciprocating means, a gear engaging said rack, an arm connected to said gear and resilient means between said arm and the support for the helical gear to absorb any uneven forces.

2. In a gear lapping machine, a lap, means for supporting said lap, means for supporting a helical gear in mesh with said lap, means for rotating one of said lap supporting and gear supporting means, said means for rotating one of said lap supporting and gear supporting means rotating the other f said lap supporting and gear supporting means through inter-engagement of the lap and gear, means for reciprocating said means for rotating one of said lap supporting and gear supporting means, and means for rocking the helical gear through an angle determined by the lead of the teeth of the lap and gear in timed relation with the reciprocation of said rotated means comprising, a rack connected with the reciprocating means, a gear engaging said rack, an arcuate member fixed to said gear, an arm adjustably connected to said arcuate member, a sleeve connected to said arm, a first spider, an adjustable clutch between said sleeve and said first spider, a second spider,

springs between the arms of said first and secmeans for moving said spindle and units supported thereby, means for moving said upper unit with respect to the lower, a pivotal support for said spindle and adjustable means for moving said spindle about said pivot.

4. A lapping machine as in claim 3, in which the means for moving the upper unit with respect to the lower comprises a cylinder fixed to said upper unit, a fluid operated piston Within said cylinder, a rod having a rack at the lower end thereof, a gear driven by said rack, a shaft on which gear is fixed, a gear driven by said shaft and rack teeth formed on said spindle engaged by said last mentioned gear.

5. In a gear lapping machine for helical gears, a lap having helical teeth, a support for said lap, means for reciprocating said support, upper and lower means for supporting a helical gear in mesh with said lap, and means forrocking said gear in timed relation with the reciprocation of said support which comprises, a rack, a gear actuated thereby and means driven by the last mentioned gear to rock the upper means for supporting a helical gear in mesh with said lap.

6. In a gear lapping machine for helical gears, upper and lower center units for a helical gear to be lapped, a lap having helical teeth in mesh with the helical gear teeth, a support for said lap,

means for reciprocating said support and lap carried thereby, means for moving the upper center unit with respect to the lower, a rack driven in timed relation with said reciprocation, a gear mounted on said upper center unit and driven by said rack, said rack being of such length that the rack and gear are in mesh during movement of the upper center unit with respect to the lower, and means actuated by the gear on the upper center unit for rocking the helical gear to be lapped in timed relation with the reciprocation of the lap.

7. In a lapping machine, a support, upper and lower centers carried thereby, said centers supporting a helical gear, means for moving the support and upper and lower centers as a unit, means for moving the upper center withrespect to the lower, asleeve, a lapping ring fixed to said sleeve and meshing with the helical gear to be lapped, means to rotate said sleeve and lapping ring, means to reciprocate said-sleeve and lapping ring, resilient means for damping vibration of the reciprocating parts, a rod having one end connected to said reciprocating means and having its other end formed with a rack, a gear mounted for movement with the upper center and having meshing engagement with the rack, said rack being of such length that the engagement with the gear is maintained during movement of the upper center with respect to the lower, an arcuate member fixed to the gear, a sleeve, a rod having one end adjustably secured to the arcuate member and its other end connected to 'the sleeve, aslidable' clutch actuated by the sleeve, a shaft for rocking the gear to be lapped, and resilient means between the clutch and shaft to absorb any uneven forces. I

8. In a gear lapping machine, alap for a helical 7 gear, a support therefor, a support for maintaining a helical gear in mesh with the lap, means for reciprocating one of said supports with respect to the other and means including a rack and gear for oscillating one of the gear and lap supports through an angle determined by the lead of the teeth of the lap andgear in timed relation with the reciprocation, said rack being driven by said means for reciprocating.

9. A device as in claim 8, which includes means for moving the support for the helical gear with respect to the lap.

10. In a gear lapping machine, a lapping ring having internal helical teeth, a support for said lapping ring, means for maintaining a gear to be lapped having a lesser number of teeth than the lapping ring in mesh therewith, means for rotating said lapping ring support, means for reciprocating said support while it is rotating, and means driven by said reciprocating means for oscillating a gear to be lapped in timed relation with the reciprocation.

11. In a gear lapping machine as in clainr 10, in which the last. mentioned means includes a rack driven by said reciprocating means and a gear meshing therewith.

12. A gear lapping machine as in claim--10,

which includes resilient adjustable stops for maintaining the gear in mesh with the lapping ring.

. 13. Ina. gear lapping machine, a lapping ring for a helical gear, a support therefor, two centers for supporting a helical gear in mesh'with the lapping ring, means for rotating the lapping ring to rotate said gear, means ,for reciprocating the lapping ring with respect to said gear, means for moving one of said centers with respect to the other, and means to oscillate a gear to be lapped in timed relation with the reciprocation comprising, a rack movable with the reciprocating means and a gear engaging said rack and mounted for movement with one of said centers, said rack being of sufllcient length to remain in engagement with the gear during movement of the latter with the center.

14. In a ,gear lapping machine, a spindle, an upper center unit and a lower center unit supported by said spindle, means for moving said spindle and units supported thereby, and means for movingsaid upper unit with respect tothelower comprising a cylinder fixed to said upper unit, a fluid operated piston within said cylinder,

a rod having a rack at the lower end thereof, a .gear. driven by said rack, a shaft on which a gear is fixed, a gear driven by said shaft and rack teeth formed on said spindle engaged by said last mentioned gear.

15. In a gear lapping machine, a lap, means supporting said lap, a spindle, an upper center unit and a lower center unit supported by said spindle, said units supporting a gear to be lapped in mesh with the lap, one of the lap and gear being a ring member having internal teeth and the other of the lap and gear having a lesser number of teeth than does the ring member, means for moving said spindle and units supported thereby, means for moving said upper unit with respect to the lower, a pivotal support for said spindle in substantially the plane 01' the lap and adjustable means for moving said spindle about said pivot.

EDWARD R. NYLAND.- 

